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Old 03-28-2021, 02:38 PM   #1
Greasey Harley
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alternators: 10si vs 12si wiring

I know this has been covered extensively however, I've have been looking and am still a little fuzzy.
I'm looking to upgrade from an externally regulated 10dn to an internally regulated unit.
Looks like 10si alternator can be installed with a jumper wire at the regulator and a plug swap at the alternator.

When I lookup 12si conversion:
Some claim you can install a 12si with the same simple mod.
Some say you need to cut into the harness.

...Or am I reading that wrong?
does a 12si wire up the same as a 10si?

I don't need more amps than a 10si will provide and I don't want to chop into my harness right now.
That being said, If I can install a 12si without rewiring, obviously I will.

Thanks,
-Russ
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Old 03-28-2021, 03:29 PM   #2
Dead Parrot
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Re: alternators: 10si vs 12si wiring

I swapped a 12si in place of a 10si on my 75 C10. Drop in replacement. No changes needed. I did it because the 12si puts out a few more amps at idle speed and largely gets rid of the dim down effect when you stop while headlights, blower motor and wipers are all running. Like you, I didn't need the increased max output.
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Old 04-03-2021, 09:57 PM   #3
Greasey Harley
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Re: alternators: 10si vs 12si wiring

Decided to go with 63 amp 10si, it just looks correcter.
Guess I'm going to do a quick rewire while I'm in there too. I wanted to avoid opening up the wiring harness, but my CDO [properly alphabetized] won't let me leave jumper wires under the hood.
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Old 04-05-2021, 03:32 PM   #4
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Re: alternators: 10si vs 12si wiring

Quote:
Originally Posted by Greasey Harley View Post
Decided to go with 63 amp 10si, it just looks correcter.
Guess I'm going to do a quick rewire while I'm in there too. I wanted to avoid opening up the wiring harness, but my CDO [properly alphabetized] won't let me leave jumper wires under the hood.

You should read my thread in the electrical forum stickies on frequently asked questions. It contains a lot of info on converting to internally regulated alternators.
I think you are telling us you are OCD not CDO but I could be wrong. VV
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Old 04-05-2021, 08:25 PM   #5
Greasey Harley
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Re: alternators: 10si vs 12si wiring

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Originally Posted by VetteVet View Post
You should read my thread in the electrical forum stickies on frequently asked questions. It contains a lot of info on converting to internally regulated alternators.
I think you are telling us you are OCD not CDO but I could be wrong. VV
I found that sticky after I posted this, thanks for all the information.
I got it done and am happy with the results. The wiring defiantly needed some attention.Name:  IMG_20210404_195726761.jpg
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